Well you might have not read the experience where an applicant received a procedural fairness letter for the work experience which was not mentioned his/her previous applications (study and work permit) but suddenly on PR file was mentioned.
So this is not correct that they are only looking for rejection reason from past. They align all the info you are providing to them are consistent or not.
They are giving you Permanent Residency which is kind of the big deal for any country and they will thoroughly examine very bit of info you provide to them.
I explicitly mentioned rejection or any other reason to compare.The last I checked that was not written in Swahili so I don't understand the "not correct" part.I am not going to list out every episode of the series to explain how comparisons are made...